Electronic Telegram No. 2983
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2012G
     W. Zheng, University of Michigan; J. Vinko, University of Szeged; G. H.
Marion, Harvard-Smithsonian Center for Astrophysics; R. Quimby, IPMU,
University of Tokyo; N. Whallon, A. Romadan, N. Wagner, and C. Akerlof,
University of Michigan; F. Yuan, Australian National University; and J. C.
Wheeler and E. Chatzopoulos, University of Texas, on behalf of the ROTSE
collaboration, report the discovery of a new supernova (mag about 16.5) in
unfiltered images taken on Jan. 14.37 UT with the 0.45-m ROTSE-IIIb telescope
at McDonald Observatory.  The transient was observed again at mag about 16.0
on Jan. 15.37 and 18.37, with no detection before Jan. 7 down to a limiting
magnitude of about 18.2.  The new object is located at R.A. = 12h39m35s.1,
Decl. = +16o35'11".9 (equinox 2000.0; uncertainty about 1"), which is 10".7
west and 4".3 south of the proposed host galaxy (SDSS J123935.85+163516.1,
whose SDSS redshift is z = 0.026); a finding chart is posted at website URL
http://www.rotse.net/rsvp/j123935.1+163512/ROTSE3_J123935.1+163512.jpg.
     A spectrum, obtained on Jan. 16.38 UT with the 9.2-m Hobby-Eberly
Telescope (+ Marcario Low-Resolution Spectrograph) by S. Odewahn, shows
that 2012G is a type-Ia supernova about one week before maximum brightness.
According to SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), the spectrum
resembles that of SN 2003kf at nine days before maximum.  Adopting a
redshift of 0.025, measured from host-galaxy emission lines, the
velocity from the absorption minimum of the Si II 635.5-nm feature is
10500 km/s.  The Ca II infrared-triplet feature displays a high-velocity
component at 22500 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 January 20                  (CBET 2983)              Daniel W. E. Green